For 63 years the body of James Austin Sisney lay on a remote Pacific island, visited only by the natives who live near the mountain where the Redwood City man’s Marine bomber crashed during World War II.

Sisney and six other crew members died April 22, 1944, when their twin-engine plane slammed into a cliff face during a night training mission above Espiritu Santo, the largest island in the South Pacific archipelago now known as Vanuatu.

That information never reached the men’s loved ones, however. A military report on the crash disappeared amid the confusion of war, and the whereabouts of the plane became a mystery. Some families thought it had gone down in the ocean. They didn’t learn the truth until several years ago, when a persistent relative of one of the crew members discovered the crash site.

As a result of that endeavor, Tech. Sgt. Sisney will return next week to the country he died protecting. A portion of his remains will be buried Friday with full military honors at Golden Gate National Cemetery in San Bruno. A ceremony for the entire crew will take place in October at Arlington National Cemetery in Virginia.

“I guess you could say it’s a little bit of closure,” said Robert Sisney Jr., of Sunnyvale, the man’s nephew and one of a handful of surviving relatives. He, his sister and half-sister will greet their uncle’s flag-draped coffin Thursday at San Francisco International Airport.

Robert Sisney Jr., 48, doesn’t know much about his uncle, who died two decades before he was born. Robert’s father, who was James’ only sibling, was a man of few words and he didn’t volunteer information about the war.

Robert, a construction worker, said James Sisney spent the first years of his life in Livermore. The family later moved to Redwood City, and James graduated from Sequoia High School in 1942.

Marguerite Richardson, 88, was a member of that graduating class. She remembers him as a tall, quiet redhead.

“Not in any trouble,” Richardson said. “Just did his work.”

James joined the Marines in December 1942 at age 17. He was sent to the Pacific theater, where he became part of a bombing squadron known as the Seahorse Marines.

He was just 19 when his PBJ-1D, a version of the B-25 bomber, failed to clear the summit of a mountain that rises more than 3,000 feet above the idyllic beaches of Espiritu Santo.

Maj. John Palmer, commander of the aircraft group, learned of the wreckage a month later. He and a team of men, guided by natives, made the arduous hike up the steep, tangled mountainside to examine the plane.

“It obviously exploded upon impact, instantly killing all personnel, and then burned,” Roberts wrote in the report, unearthed more than a decade ago by a former Marine pilot, Dan Bookout. The team found human remains and buried them near the wreckage, which over the years was engulfed by the jungle and forgotten by all but the natives, for whom the wreck remained a piece of local lore.

That’s how it stayed until 2007, when a Texas man, Craig Anderson, and his wife, Kim, clawed up the mountain with their daughter and son-in-law and a handful of native men.

Craig Anderson had begun researching Kim’s late uncle, 2nd Lt. Walter B. Vincent Jr., in 2005. He eventually tracked down Bookout, who had come across the bomber that carried both Sisney and Vincent while investigating a different crash in the area.

“I remember thinking, if I was to find the location of this plane, I’d just have to look at it,” Craig recalled.

That determination yielded the exhilarating moment in early June 2007 when the Andersons glimpsed a rusty propeller sticking out of the underbrush. Identifying numbers on the plane proved they had found the resting place of Vincent, Sisney and their comrades.

When they returned, they contacted the Joint POW/MIA Accounting Command in Hawaii, the military outfit responsible for tracking down missing servicemen and -women. The command excavated the site, and DNA samples confirmed the identities of the crew.

James Sisney will receive his long-overdue honors beginning Thursday when a group of Patriot Guard Riders escort his casket — containing a uniform, medals and two pieces of his right arm — from the airport to a Sunnyvale mortuary.

On Friday he will be interred at Golden Gate National Cemetery underneath a headstone he received after he was reported missing in action and presumed dead.

Robert said his father, who learned the truth about his brother’s death shortly before he passed away in 2010, would have been bothered by the pomp and circumstance. But Robert is grateful for the support his family has gotten — from veterans and their kin, from the military, and from the riders.